This invention relates to an apparatus for measuring the ratio of two pressures.
The patents to Hartig et al., U.S. Pat. No. 1,881,543; Hartig, U.S. Pat. Nos. 2,015,933; and 2,151,203; Wolff, U.S. Pat. No. 2,274,262; Welkowitz, U.S. Pat. No. 2,959,054; and Liston et al., U.S. Pat. No. 3,443,433, disclose various types of flow meters. Devices which use fluidic signals to indicate flow are described in the patent to Beeken, U.S. Pat. No. 3,600,612, and in an article by Bernard Vonnegut, "A Vortex Whistle", in The Journal of the Acoustical Society of America, Volume 26, Number 1, January 1954.